The Bulletin of The Korean Astronomical Society (천문학회보)
- Volume 46 Issue 1
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- Pages.46.1-46.1
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- 2021
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- 1226-2692(pISSN)
Study of Hydrated Asteroids via Polarimetry: Correlation between Polarimetric Properties and the Degree of Aqueous Alteration of Hydrated asteroids
편광을 통한 수화한 소행성 연구
- Geem, Jooyeon (Seoul National University) ;
- Ishiguro, Masateru (Seoul National University) ;
- Naito, Hiroyuki (Nayoro Observatory) ;
- Kuroda, Daisuke (Kyoto University) ;
- Takahashi, Koki (Hokkaido University of Education) ;
- Sekiguchi, Tomohiko (Hokkaido University of Education) ;
- Takagi, Seiko (Hokkaido University) ;
- Ono, Tatsuharu (Hokkaido University) ;
- Kuramoto, Kiyoshi (Hokkaido University) ;
- Nakamura, Tomoki (Tohoku University)
- 김주연 (서울대학교) ;
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- Published : 2021.04.13
Abstract
Hydrated asteroids get widespread attention for the evolution of water in the Solar System, especially thanks to the recent successes of the Hayabusa2 and OSIRIS-REx space missions. The target asteroids of these missions are believed to be fragments that have experienced aqueous alteration in their parent bodies [3]. Although hydrated asteroids have been studied well via spectroscopy, focusing on the 0.7 um or the 2.7 um absorption bands [2, 3, 4], polarimetric properties of these asteroids have rarely been investigated. In this study, we conducted a polarimetric observation of 18 C-complex main-belt asteroids with the 1.6-m Pirka telescope at the Nayoro Observatory of Hokkaido University, Japan. We used a polarimetric imaging mode of the Multi-Spectral Imager (MSI) with the standard Rc-band filter (the central wavelength at 0.64 um) [5]. As a result, we found that all of these hydrated asteroids indicate deep negative branches of their polarimetric profiles. Accordingly, the hydrated asteroids have the polarization minima (Pmin), whose values are significantly lower than any other taxonomic types of asteroids (including C-group asteroids). Because Pmin depends on albedo, particle size, and porosity of the surface materials [1], we suspect that hydrated asteroids are distinctive from other asteroids in terms of these physical properties. In this presentation, we introduce our polarimetric observation and findings. We discuss why hydrated asteroids indicate such low Pmin values, comparing Pmin with spectral features at 0.7 um and 2.7 um based on the observation results.
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